HP procurve 8100fl series Management And Configuration Manual page 140

Spanning-Tree Operation
Configuring MSTP
9-24
Syntax: spanning-tree priority <priority-multiplier >
This command is used within the spanning-tree instance
configuration context and sets the switch (bridge) priority for the
designated instance. This priority is compared with the priorities of
other switches in the same instance to determine the root switch for
the instance. The lowest priority value determines the root. (If there
is only one switch in the instance, then that switch is the root switch
for the instance.) The root bridge in a given instance provides the
path to connected instances in other regions that share one or more
of the same VLAN(s). (Traffic in VLANs assigned to a numbered STP
instance in a given region moves to other regions through the root
switch for that instance.)
The priority range for an MSTP switch is 0-61440. However, this
command specifies the priority as a multiplier (0 - 15) of 4096. That
is, when you specify a priority multiplier value of 0 - 15, the actual
priority assigned to the switch for the specified MST instance is:
For example, if you configure "5" as the priority-multiplier for MST
Instance 1 on a given MSTP switch, then the Switch Priority setting is
20,480 for that instance in that switch.
Note: If multiple switches in the same MST instance have the same
priority setting, then the switch with the lowest MAC address becomes
the root switch for that instance.
(priority-multiplier) x 4096